Characterization of electrodeposited Ni-Cr/hBN composite coatings

In this study, Ni-Cr/hBN composite coatings with different hBN content were deposited on AISI 1040 mild carbon steel using electrodeposition. The coatings were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD), cyclic voltammetry (CV), 2D surface profilometery, nano-indentation, corrosion and wear tests. While some cracks were observed in the Ni-Cr alloy coatings, more compact and crack-free surfaces were obtained in the Ni-Cr/hBN composite coatings under all deposition conditions. XRD analysis of the Ni-Cr/hBN layer revealed the presence of a predominant Ni phase with Cr, Cr2Ni3B6, (Ni2Cr23)(0.16), and hBN phases in the structure. Depending on deposition parameters, the microhardness and nanohardness of the Ni-Cr and Ni-Cr/hBN coatings were found to range between 308 and 538 HV and 1,86-7,69 GPa respectively. hBN acted as a solid lubricant in the wear tests; the friction coefficient decreased and wear resistance was improved. Among the composite coatings, the corrosion resistance of the coating with 20 g/l hBN was found to be 12 and 3.3 times higher than the steel substrate and Ni-Cr alloy, respectively. The hBN additive provided better mechanical properties and corrosion resistance in the range of 5-20 g/l hBN, but after 20 g/l hBN agglomeration became a problem and impaired the mechanical properties. The highest corrosion and abrasion resistance was obtained with 20 g/l hBN. (c) 2020 Elsevier B.V. All rights reserved.